@book{Pooten2009,
  author    = {Pooten, Holger},
  title     = {Grundlagen der Bilanzanalyse},
  edition   = {Lektion 2},
  year      = {2009},
  language  = {de}
}
@book{Pooten2009,
  author    = {Pooten, Holger},
  title     = {F{\"u}hrungswissen f{\"u}r Ingenieure},
  edition   = {Lektion 3},
  year      = {2009},
  language  = {de}
}